The present invention relates to power semiconductor devices and a method of fabricating a power semiconductor device.
MOSgated devices, such as power MOSFETs and IGBTs are very well known, and have a gate electrode, usually made of conductive polysilicon, which must be electrically insulated from the source electrode (or emitter electrode) and yet must be electrically connected to an external metallic gate conductor or gate pad, usually of aluminum. In a self aligned contact power MOSFET, contact to the source is made in the active area, using spacer technology. However, the gate metal-to-gate polysilicon contact at the gate pad has required the use of a separate photo mask step.
U.S. Pat. No. 6,893,923, assigned to the assignee of the present application, discloses a power MOSFET (FIG. 1) which includes a recess formed in the field oxide in the termination region thereof. The recess is formed during the active mask step in which the field oxide layer is etched to define the active area and the bottom thereof is oxidized during the gate oxidation step. Thus, the oxide in the bottom of the recess is the same thickness as the gate oxide in the device.
The present invention provides certain improvements over the process and the device disclosed in the prior art.